1. Field of the Invention
The present invention relates to an optical module and a fiber sheet for use in assembly of the optical module.
2. Description of the Related Art
A fiber sheet having a resin sheet and an optical fiber preliminarily wired on the resin sheet so as to correspond to the connecting relation between optical components is used in an optical module, printed circuit board, or optical transmission apparatus. The present invention relates more particularly to an optical module structure using a fiber sheet for fusion-splice optical fibers between optical components with a short fiber length, thereby eliminating forming of the optical fibers and making the fusion splicing efficient.
In a conventional method of assembling an optical module such as an optical amplifier, optical fibers extending from optical components are routed to connection points and forming of the optical fibers is next performed prior to the fusion splicing. As the number of optical components increases, the routing of optical fibers become more complicated and the connection of optical fibers also becomes more troublesome because of increased connection points and precise position adjustment between optical fibers to be connected. To make the assembly of an optical module efficient, the use of a fiber sheet in the optical module is being considered. The conventional fiber sheet is formed by preparing a first resin sheet having an adhesive layer on one side, bonding an optical fiber through the adhesive layer to the first resin sheet by applying a pressure to thereby wire the optical fiber on the first resin sheet, and attaching a second resin sheet to the first resin sheet so that the optical fiber is sandwiched therebetween. Thus, the adhesive layer is formed on the entire surface of the first resin sheet, so that the optical fiber sandwiched between the first and second resin sheets is fixed.
As mentioned above, in assembling an optical module without the use of a fiber sheet, the routing of optical fibers becomes more complicated and the connection of optical fibers also becomes more troublesome because of increased connection points and precise position adjustment between optical fibers to be connected as the number of optical components increases. Further, the troublesomeness of fiber connection makes it difficult to automate the connection work. On the other hand, in the case of assembling an optical module by using a fiber sheet, an optical fiber extending from the fiber sheet is connected to an optical fiber extending from an optical component. At this time, it is sometimes preferable to reduce the length of each optical fiber from the viewpoints of mounting limitation and workability.
In this case, an extra fiber length due to variations in length of each optical fiber causes a bend and/or stress in the optical fiber at its spliced portion. It is therefore necessary to adjust the extra fiber length. However, in the conventional fiber sheet, the optical fiber is completely fixed between the first and second resin sheets, so that the extra fiber length cannot be adjusted after wiring the optical fiber.